Muharram (Arabic: محرم) is the first month of the Islamic calendar. It is one of the four sacred months of the year in which fighting is prohibited. Since the Islamic calendar is lunar, Muharram moves from year to year when compared with the Gregorian calendar.[citation needed] Muharram is so called because it was unlawful to fight during this month; the word is derived from the word ‘haram’ meaning forbidden. It is held to be the most sacred of all the months, excluding Ramadan. Some Muslims fast during these days. The tenth day of Muharram is called Yaumu-l 'Ashurah, meaning, ‘the day of grief’. Fasting differs among the Muslim groupings; mainstream Shia Muslims stop eating and drinking during sunlight hours and do not eat until late afternoon. Sunni Muslims also fast during Muharram and on either the ninth or the eleventh day, the choice of which additional day being at the discretion of the individual. Shia Muslims do so to replicate the sufferings of Imam Hussain (A.S) on the day of Ashurah.

The word "Muharram" is often considered synonymous with the event of Ashura. Ashura, which literally means "grief" in Arabic, refers to the tenth day of Muharram. The date is important for all Muslims especially Shias since Hussein bin Ali, the 3rd Imam of Shiism, was killed on this day.